4 replies to this topic

[popay73]

Hi, I'm a bit confused about Flow units. As far as I know Flow unit is usually m^3/h in SI. In process simulators I saw Flow unit: kgmol/h. Where does this unit come from, makes no sense to me ?

Thx in advance !

[Art Montemayor]

Popay:

Flow units may usually be expressed as m³/h in the SI syteme, but they are expressed in many other units as well – mols/h, Scfh, Scfd, lb mol/h, and even kg mol/h.

Your term, kgmol/h, obviously comes from the fact that your material balance is in metric units and, therefore, you are dealing in kg mols. If you had a Process Flow Diagram with a corresponding mass balance table here in Houston, Texas, the odds are that it would reflect lb mol/h or Scfd.

Does it make sense now?

[popay73]

Thx for reply, but I'm still confused. I know there are types of flow units like m^3/h, kg/h, kmol/h...something / time.
But where does kg*mol term come from, what does it mean, how do I convert it to other units ?

As far as I know n= m / M, vol.flow = V / t, vol.flow = A * v, mass.flow = m / t, etc...but I've never heared we can multiply kg and moles.

Still confused :-)

[Austro]

Thx for reply, but I'm still confused. I know there are types of flow units like m^3/h, kg/h, kmol/h...something / time.
But where does kg*mol term come from, what does it mean, how do I convert it to other units ?

As far as I know n= m / M, vol.flow = V / t, vol.flow = A * v, mass.flow = m / t, etc...but I've never heared we can multiply kg and moles.

Still confused :-)

you know that a mol is just a number right? A kg mol is the number of molecules equal to one kilogram in mass rather than one gram in mass. It is 1000 times greater than a gram-mole.

[gvdlans]

From wikipedia.org (search for mole):
"Scientists and engineers (chemical engineers in particular) sometimes measure amount of substance in units of gram-moles, kilogram-moles, pound-moles, or ounce-moles; these measure the quantity of a substance whose mass in grams, kilograms, pounds, or ounces (respectively) is equal to its formula weight. The SI mole is identical to the gram-mole."

Therefore, the SI kmol is identical to the kgmol.